Fabrication and mechanical behavior of 2D-C _f/Ta _x Hf _{1− x} C–SiC composites by a low temperature and highly-efficient route

C_f/Ta_xHf_1-xC-SiC composites are ideal thermal structural materials for service under extremely conditions of hypersonic vehicles. However, how to synthesis Ta_xHf_1-xC powders and efficiently fabricate C_f/Ta_xHf_1-xC-SiC composites still faces some challenges. Furthermore, the mechanical properties and thermophysical properties of Ta_xHf_1-xC vary with the composition, but not monotonically. In-depth analysis of the mechanical behavior of the C_f/Ta_xHf_1-xC-SiC composites is extremely important for their development and application. In this study, Ta_xHf_1-xC powders (x=0.2, 0.5, 0.8) were successfully synthesized via solid solution of TaC and HfC at a relatively low temperature of 1800 °C, with a small amount of Si as additive. Subsequently, the efficient fabrication of 2D-C_f/Ta_xHf_1-xC-SiC composites was achieved by slurry impregnation and lamination (SIL) combined with precursor infiltration and pyrolysis (PIP). In addition, mechanical behavior of the composites was investigated systematically. It is demonstrated that the composites present remarkable non-brittle fracture, including a large number of fibers pull-out and interphase debonding. And the fracture failure involves a complex process of microcrack generation and propagation, matrix cracking and layer fracture. Moreover, the interfacial bonding between the fibers and matrix is enhanced as Ta: Hf ratio decreases from 4:1 to 1:4. As a result, C_f/Ta_0.2Hf_0.8C-SiC composite exhibits an exceptional flexural strength of 437 ± 19 MPa, improved by 46% compared with C_f/Ta_0.8Hf_0.2C-SiC (299 ± 19 MPa). This study provides a new perception for the design and fabrication of ultra-high temperature ceramic matrix composites with high performance.